The present invention relates to image processing apparatus and method and recording medium for controlling positions of dots constructing image information in pseudo halftone representation.
In recent years, an image in pseudo halftone representation is widely used upon printing by an ink-jet printer or the like. By virtue of high-speed computer processing and advanced printing technology, high-resolution and pseudo halftone multilevel representation have been achieved, and further, various schemes for pseudo halftone processing have been proposed.
In addition to the above-described improvements in quality of printed image, various purposes of image have been proposed. For example, proposed are schemes for embedding information (bits) different from an original image by e.g. adding a particular frequency component (dot pattern) to a particular region of image information or adding an image including a particular dot arrangement to the image information.
However, in the conventional art, in a low density region of pseudo-halftone processed image, the number of dots constructing the image region is extremely small. Accordingly, in such image region having a density equal to or less than a predetermined level, it is difficult to add an image including a particular frequency component in a manner the added image is inconspicuous by using the dots or form a particular dot arrangement.
On the other hand, in an image region of a density higher than the predetermined level, the number of dots constructing the image region is extremely large. Accordingly, a region to which dots can be newly added is limited, and it is difficult to add a dot pattern having a frequency component which can be extracted later to such image region or to form a particular dot arrangement. For example, in an ink-jet printer, as the size of dots to be added may increase in comparison with the resolution of image to which the dots are to be arranged, it is difficult to discriminate the added dots in an image region having a density equal to or greater than a predetermined level.
The present invention has been made in consideration of the above conventional art, and has its object to provide image processing apparatus and method and recording medium for dot arrangement control in image information in pseudo halftone representation while eliminating a density region where a predetermined dot pattern cannot be easily embedded.
Further, another object of the present invention is to provide image processing apparatus and method and recording medium for easily embedding a predetermined dot pattern in quantized image information by converting pixel values of the image information such that the pixel values stand within a predetermined range and then quantizing the image information.
In order to attain the above described objects, the image processing apparatus of the present invention comprises; pixel value conversion means for converting an input pixel value of input image information to a pixel value within a predetermined range; quantization means for quantizing the pixel value of a pixel of interest of the image information converted by the pixel value conversion means; and dot position control means for controlling a dot position of a dot formed by an image forming apparatus based on the image information quantized by the quantization means.
In order to attain the above described objects, the image processing apparatus of the present invention comprises; pixel value conversion means for converting an input pixel value of input image data to a pixel value within a predetermined range; quantization means for quantizing the pixel value of a pixel of interest of image data converted by the pixel value conversion means; and dot arrangement control means for controlling a dot arrangement for forming an image corresponding to the image data so as to form a predetermined dot pattern in the image data quantized by the quantization means.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same name or similar parts throughout the figures thereof.